FieldCache.getBytes(IndexReader reader,
String field,
FieldCache.ByteParser parser)
Checks the internal cache for an appropriate entry, and if none is found,
reads the terms in field as bytes and returns an array of
size reader.maxDoc() of the value each document has in the
given field.

byte[]

FieldCache.getBytes(IndexReader reader,
String field,
FieldCache.ByteParser parser,
boolean setDocsWithField)
Checks the internal cache for an appropriate entry, and if none is found,
reads the terms in field as bytes and returns an array of
size reader.maxDoc() of the value each document has in the
given field.